1. Field of the Invention
The invention relates to glass powder, especially biologically active glass powder, and a method to produce glass powder, especially biologically active glass powder.
2. Description of the Related Art
Biologically active glass powders in the form of bio-active glass powders are already known from U.S. Pat. No. 5,074,916 and in the form of anti-microbial active glass powders from WO 03/018499. The glass powders include a plurality of glass particles of any shape including spherical as well as non-spherical particles, for example in the form of glass fibers. The production of particles of this type may occur in different methods, whereby the glass is generally melted and converted to a semi-finished state or to ribbons which are then ground to a certain granular size. It has been demonstrated that the biological effectiveness is greatly dependent upon the particle size which manifests in an accordingly high degree of grinding.
Methods for producing particles from a melt, especially from a mineral or glass melt are known in a plurality of implementations. For example, in one of the methods for the production of glass wool for insulating purposes which is described in documentation EP 13 60 152 and EP 09 31 027 the glass melt is put into a rotating drum which is equipped with small diameter holes that are located in the wall which forms the surface area. Due to the centrifugal forces the glass melt is forced through the small holes. A significant disadvantage associated with the use of rotating elements of this type is that they are subjected to especially high wear and tear in the hot area due to the necessarily high rotational speed, thereby providing only a relatively low life span of such units.
A method for producing metallic glass powders is already known from U.S. Pat. No. 4,386,896. In this method, the glass melt is atomized under the influence of moving elements and a gas and is directed toward a centrifuge disk. The described atomizing methods include a single substance nozzle as well as the use of cold gas. Also in this scenario the mechanical elements of the apparatus which are necessary for the atomization are also exposed to the high temperatures of the glass melt, resulting in high maintenance of this type of apparatus. In addition, the throughput is determined by the speed of the motion and the rotational speed of the rotating elements.
A method for atomizing of metal melts which utilizes two nozzles in the atomization area is described in WO 98/12116. Here, a first nozzle unit is utilized for atomizing and a second nozzle for providing the cold gas in order to cool the created droplets. In contrast, DE 100 02 394 C1 discloses a method for the atomization of melts utilizing hot gas in order to produce spherical particles. Here, a melt having a dynamic viscosity η in the range between 0.01 and 100 Ns/m2 is produced. The molten stream is atomized utilizing a primary gas, whereby the primary gas has a temperature of at least TA=TG 
TG=Glass forming temperature
TA=Glass exit temperature
at the nozzle discharge point. Cooling of the particles which were formed during atomizing occurs in a cooling zone downstream from the nozzle in the production flow through utilization of a quenching medium, whereby the temperature of the quenching medium is lower than the temperature of the glass forming temperature. In this method the glass melt stream is led over a certain distance and the primary gas is supplied through several individual nozzles. This supply method over a long period of time avoids cooling and favors the formation of spherical particles. Particles of this type however, do not fulfill the demands put upon biologically active glasses which must be characterized by a high biological effectiveness.
What is needed in the art is to develop a glass powder, especially a biologically highly active glass powder, as well as a method to produce a glass powder, especially a biologically highly active glass powder which is characterized by a high throughput combined with low thermal and mechanical demand upon the elements which are associated with the particle formation, as well as by a favorable energy balance. The construction and controls related expenditure should be kept as low as possible.